captchas are used to scan books into digital form of the captcha is a known sequence of numbersletters and the other is a scanned document the idea is to use the power of social networks to perform a task that would normally take decades of careful scanning getting books scanned into an electronic form is now an easy process thanks to captcha the idea of typing the second half as nigger is that well start ruining captcha and there will be whole pdfs out there filled with nothing but pages of nigger